First one-line mass measurements at SHIPTRAP and mass determinations of neutron-rich Fr and Ra isotopes at ISOLTRAP

SHIPTRAP is an ion trap facility behind the velocity lter SHIP at GSI/Darmstadt. Its aim are precision studies of transuranium nuclides produced in a fusion reaction and separated by SHIP. The current set-up for high-precision mass measurements consists of three main functional parts: (i) a gas cell for stopping the energetic ions from SHIP, (ii) radiofrequency quadrupole structures to cool and to bunch the ions extracted from the gas cell, and (iii) a superconducting magnet with two cylindrical Penning traps at a eld strength of 7 T. In this work the Penning trap system has been installed and extensively characterized. The rst on-line mass measurements of short-lived nuclides were carried out and the masses of 147Er and 148Er could be experimentally determined for the rst time. Here a relative mass uncertainty of δm/m of about 1 x 10-6 was achieved. Furthermore the masses of heavy neutron-rich 229-232Ra and 230Fr isotopes have been determined with a relative mass uncertainty of about 1 x 10-7 with the ISOLTRAP mass spectometer at ISOLDE/CERN. The isotope 232Ra is the heaviest unstable nuclide ever investigated with a Penning trap. Underlying nuclear structure effects of these nuclides far from β-stability were studied by a comparison of the resulting two-neutron separation energies S2n with those given by the theoretical Infinite Nuclear Mass model. (orig.)